Diet associations in endometriosis: a critical narrative assessment with special reference to gluten.

Endometriosis is characterized by the presence of endometrium-like tissue outside the uterus. The etiology remains largely unknown. Despite adequate treatment, patients can still experience symptoms or side effects resulting in therapy incompliance and in self-management strategies such as dietary measures is increasing. A gluten free diet is thought to be contributory in reducing endometriosis-related pain, thereby optimizing quality of life. However, data is conflicting and currently provides no evidence for causality. This narrative review aims to put the effect of dietary self-management strategies on endometriosis in a balanced perspective, especially the effect of gluten and a gluten free diet. Several studies have found a strong overlap in symptoms, metabolic and immune responses associated with endometriosis and those associated with celiac disease, ulcerative colitis, Crohn's disease, irritable bowel syndrome and non-celiac wheat sensitivity. However, it remains unclear whether these diseases and/or disorders are causal to an increased risk of endometriosis. Some studies have found a positive effect on the risk of endometriosis, endometriosis-related symptoms and quality of life (QoL) when women either avoided certain nutrients or foods, or applied a specific nutrient supplementation. This includes the avoidance of red meat, an increasing intake of foods rich in anti-oxidants, omega-3, micronutrients and dietary fibers (e.g., fruit, vegetables) and the appliance of a gluten free diet. However, data from the available studies were generally graded of low quality and it was noted that placebo and/or nocebo effects influenced the reported positive effects. In addition, such effects were no longer seen when adjusting for confounders such as overweight, when a translation was made from in vitro to in vivo , or when the nutrients were not supplemented as isolated sources but as part of a mixed daily diet. Finally, some studies showed that long-term adherence to a gluten free diet is often associated with an impaired diet quality and nutrient intake, leading to negative health outcomes and reduced QoL. Concluding, scientific evidence on the efficacy of dietary interventions on well-defined clinical endpoints of endometriosis is lacking and recommending a gluten free diet to women solely diagnosed with endometriosis should therefore not be advised.
Competing Interests: The authors report to have received funding for attending/speaking at conferences and/or other funding that might be perceived as potential conflict of interest, as follows: FB: travel and speaker fees in the period 2018–2020 for various conferences addressing health aspects of cereals and bread with special reference to gluten disorders in Brussels, Paris, Cappadocia, Athens, Munich, Istanbul, Wageningen, Leuven and Barcelona. AH: travel grant from Merck KGaA to visit the congress of the European Society of Human Reproduction and Embryology (ESHRE) 2022 in Milano. DK: research funding from Allergan, Will Pharma, Grunenthal, ZonMw, MDLS, UEG, Horizon 2020, Rome Foundation, all outside of submitted work. His institution has received speaker’s fee from Dr. Falk on his behalf, outside of submitted work. JM: research funding from Maxima Medical Center and ZonMw, both outside of submitted work. VM: travel and speaker’s fees from Guerbet as well as research grants from Guerbet, Merck and Ferring, all outside of submitted work. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
(Copyright © 2023 Brouns, Van Haaps, Keszthelyi, Venema, Bongers, Maas and Mijatovic.)